Trondheim historically, Nidaros and Trondhjem, is a city and municipality in Sør-Trøndelag county, Norway. With a population of 173,486, it is the third most populous municipality and city in the country, although the fourth largest metropolitan area. It is the administrative center of Sør-Trøndelag county. Trondheim lies on the south shore of the Trondheimsfjord at the mouth of the river Nidelva. The city is dominated by the Norwegian University of Science and Technology (NTNU), SINTEF, St. Olavs University Hospital and other technology-oriented institutions.
The settlement was founded in 997 as a trading post, and was the capital of Norway during the Viking Age until 1217. From 1152 to 1537, the city was the seat of the Archdiocese of Nidaros; since it has remained the seat of the Diocese of Nidaros and the Nidaros Cathedral. It was incorporated in 1838. The current municipality dates from 1964, when Trondheim merged with Byneset, Leinstrand, Strinda and Tiller